I'm not aware of Christians mass protesting anything except abortion, so I still don't see it happening.
However, the official curriculum right now implies that Genesis is false, and does so in a way that is impossible to miss. Unless the official curriculum was altered in such a way as to make it clear that the state had adopted a position that was overtly hostile to Christianity itself, I don't imagine Christians would be more up in arms than they are now, which, really, is not all that up in arms. They grumble a lot about it, but that's about it.
OK, well of course I have been guessing that Christian fundamentalists in the US would hold huge angry street protests. So maybe I am wrong to think that. Though, I have to say that, equally you must also be guessing that it would not turn ugly.
But the reason why I think you would get serious opposition from US Christians, is partly that we do see, as you just mentioned, quite angry protests about abortion, and not just arising from the current proposals of letting individual states decide to make abortion illegal, but also before any of these current attempts to change the abortion laws, we did IIRC see a number of incidents where Christian fundamentalists have violently attacked staff at abortion clinics ... so that was one of the things in my mind ... But, also in the present discussion what have been talking about is Psion's proposal that pupils in ordinary schools all over the US should be encouraged to interrupt the teachers to dispute whether of not science effectively proves that humans evolved from earlier apes only about 200,000 years ago (that's only very recent in terms of the age of the Earth), so that biblical beliefs about God's creation are deffinitely untrue ... that would be a situation where the teachers were drawn into a direct claim of telling the class, in fact "teaching" the class, that God did not make humans and that their bible and their religious beliefs are wrong ...
... as far as I can see that would definitely lead to millions of very angry Christian parents when their kids came home from school saying that their teachers had taught them that their biblical faith was untrue about what is actually the root-&-branch basis of their faith, ie the belief that God created humans as his special project and his entire purpose in creating any universe at all ... ie, creation is, afaik, absolutely central to Christianity (and also to Islam) ... if creation is only an untrue myth, then as far as I can see the entire basis of the faith crumbles.
Anyway, the above is where I was coming from in those earlier replies, ie that's my thoughts on the entire issue as raised/proposed by Psion.